Karst in other lands: temperate regions

The best-developed karst regions of the world are found in tropical (e.g., South China and Jamaica) and temperate environments (e.g. Bosnia, Croatia, Herzegovina, Montenegro and Serbia). This may in part be due to climate, but purity limestone is also important. In this section we will examine the karst in countries that used to form Yugoslavia.

The term "karst" stems from the region Krs in Slovenia, a barren, rocky limestone area. Parts of Bosnia, Croatia, Herzegovina, Montenegro and Serbia (which used to form parts of Yugoslavia) are famous for their karst landscape, which is found in the Adriatic coastal region, the Dinaric Alps and an inner region that also stretches across the border into Romania Unlike England, where the best karst features are preserved in the massive Carboniferous limestone, in this temperate region limestones are Mesozoic (Triassic, Jurassic and Cretaceous) in age.

Karst features

'Polje' or crater-like depression in the Karst (quaternery subsidence in Trias Kalk. (Hassert.)). Cetinje. M. Burr. Aug 98. Montenegro.

Solution features in the temperate karst of the countries, formerly in Yugoslavia, show similarities to those of the Yorkshire Dales, the Peak District and the Mendip Hills. However, they are generally larger, show differences in shape and are given Slavic names such as poljes and uvalas.

Poljes

Polje

Poljes are large (at least 400 m across), closed depressions with flat floors, steep slopes up to the rim and they often have a stream flowing through them. They may be elongate (e.g. Glamoc Polje, in Croatia) and where they have coalesced, they form valleys (e.g. near Titograd). Others are more circular in outline (e.g. Lož Polje, Slovenia). Some poljes, are vast; Lika Polje, in Croatia, is over 80 km long. The Popovo Polje, Herzegovina, has a number of residual conical hills, or 'hums', penetrating through the sediment that covers the floor.

Streams may flow down the rim of the polje and cross its floor, before sinking into a low point through a cave or a sinkhole called a ponor. Some poljes have just a single stream while others (such as Kupres Polje, Bosnia) have several, each sinking into a ponor.

Uvalas

Uvalas are enclosed depressions with uneven floors that are formed by solution of the limestone. They sometimes form when several dolines join together to form a single depression and sometimes they form when small dolines form within a larger one. In areas where the limestone dips steeply down wards, elongate uvalas may develop. The Ceteniste uvala in the limestone area in south-western Serbia is a typical example.

Vruljas

There has been considerable folding and faulting of the limestones in Montenegro, particularly during the late Cretaceous and early Palaeogene. This has increased the porosity of the rock by increasing the number of fissures through which water can move. During some parts of the year considerable amounts of water disappear into the subterranean passageways. Hydrostatic pressure is high and the rivers are forced to flow below the water table. In some regions underwater springs, called vruljas, occur. Examples of vruljas are present beneath the water of Lake Skadar, Montenegro, and along the Adriatic coast.

Estavelles

Popovo Polje

Although this part of Europe is dry in the summer, during the winter there is rain, which is sometimes torrential, turning poljes into lakes. Sometimes there is so much water that the underground cave systems are totally flooded and cannot accept any more. The water backs up and at some sinkholes water is forced out of the ground. In other words, the sinkhole has reversed its role; water does not sink into it, but instead water pores out. The places where there is an alternation of inward and outward moving water are called estavelles (from the French). The Popovo Polje in Herzegovina, is about 55 km long and never more than about 4km wide and contains numerous hums, springs, ponors and estavelles.

Caves

This part of the Mediterranean is dry in the summer so that springs and streams dry up and solution of the limestone can not take place. During the winter there are rains that may result in the flooding of poljes and considerable amounts of water disappear down sinkholes into the cave systems. So solution of the limestone does not take place at a constant rate. Caves are extensive in the region. Some are extremely long, for example, the Usacka Pecina system in Serbian is over 6 km long. Pecina nad Vrazjim Firovima (which means 'Cave Over the Devil's Whirlpools) in Montenegro is over 11.75 km long (and there are many passages still to be explored). One of the deepest cave in region is Jama na Vjetrenim brdima, Montenegro, which is 897 m deep.

Precipitation features

One of the features characteristic of karst regions is the formation of stalactites, stalagmites and other speleothems, and there are many examples in the temperate regions. In Serbia, for example, the Usacka Pecina system, near the village Gornje Lopize, has many speleothems including curtains, flowstone "waterfalls" and columns up to 10 meters high, and stalactites and stalagmites of white, red or blue-grey calcite.

On the western rim of the Pester plateau, Montenegro, a gorge has been formed by the River Bistrica. There are a number of caves in the gorge, including the 'Cave Over the Devil's Whirlpools'. Here, 'Lakes Gallery' contains 15 are permanent lakes dammed by precipitated rimstone. Chemical precipitation has also created flowstones and small stalagmites and stalactites. 'Big Labyrinth' and 'Big Gallery' contain many speleothems of different shapes and colours.